Radio Frequency (RF) amplifiers, generators and matching networks are used in many applications, including telecommunication, broadcast, and industrial processing. These systems and their components can generate heat that can compromise system operation. Thus, there is a need to cool such systems.
In an RF generator, for example, an RF signal is taken at the input of the RF amplifier and this RF signal is used to modulate the power derived from the DC power supply in order to provide RF power at significantly higher power than the input. The difference between the RF output power and the DC input power is the loss within the RF generator. This loss is then dissipated as heat among the different components of the RF generator. A fan can circulate air from the outside of the RF housing into the housing and over the circuits and then purge the air from holes in the sides of the housing. For higher power RF generators, one could use a water-cooled heat sink that is situated adjacent to the power Field Effect Transistors (FET) to remove heat generated in their components. Some of the electrical circuits, however, are not mounted on the heat sink and therefore must be cooled by other means, such as air circulation that requires the use of fans in addition to the use of a water-cooled heat sink.
Similarly, for an RF matching network, the internal resistances of the components result in varying levels of heat generation in those components. Certain components may be cooled efficiently when they are mounted to a heat sink while other components can only be cooled through air flowing over those components. The heat sink in an RF matching network may be either air cooled or water cooled.
In a semiconductor manufacturing system, an RF generator delivers power to a vacuum chamber, through an RF matching network, to create a plasma. While the RF generator has internal protection circuitry that can reduce the output power or completely shut off the power if a fault occurs in the system, sometimes the reaction to a fault is not fast enough and can result in a component failure. A component's failure can result in thermal damage to the component as well as the PCB assembly or other assemblies to which it is mounted. This thermal damage can result in scorching of the component or other assemblies resulting in outgassing of material from those assemblies. If the RF generator is air cooled and has an air inlet and exhaust holes in its enclosure, the outgassed gasses and material can be ejected from the RF generator and contaminate the surrounding environment. Contamination of the surrounding environment can in turn contaminate wafers or substrates in the semiconductor fabrication plant (fab) resulting in extensive financial damage to the fab. A similar situation can result from failure of a component or assembly in an air-cooled RF matching network.
For these reasons, it is important to prevent the outgassing of gasses and material from an RF generator or an RF matching network or a combination an RF generator and an RF matching network. Additionally, to limit further damage to the RF generator and or the RF matching network, a need exists to limit or prevent further power from being dissipated into the failed component. Thus, there exists a need for an effective method for cooling enclosed systems, such as systems utilizing large power generators.